The National Labor Relations Board (NLRB) has not yet decided whether to stop planned Black Friday protests in front of Walmart stores, calling the allegations that a union is conducting illegal picketing "complex."

Walmart, the largest employer in the country with 4,000 U.S. locations, had requested last Friday that the NLRB issue an injunction against planned protests outside Walmart stores that could take place on Black Friday, one of the busiest shopping days of the year. But the NLRB Office of General Counsel said it will likely not be able to issue a decision before Thursday about the protests.

Walmart does not recognize an official workers' union and alleges that the United Food and Commercial Workers (UFCW) union is organizing illegal picketing at its stores.

Labor advocates critical of Walmart say it does not pay workers enough and many part-time workers are unable to work more hours and earn additional income.

On Tuesday evening, the NLRB said it cannot issue a decision yet because the issue is "complex." Since Monday, the labor board has investigated Walmart's allegations by speaking to the union, interviewing witnesses and sifting through documents provided by Walmart.

"The legal issues -- including questions about what constitutes picketing and whether the activity was aimed at gaining recognition for the union -- are complex," the labor board said. "Also, there are many distinct factual circumstances at stores across the country to consider."

The NLRB said it expects to complete its investigation by Wednesday.

Since October, a group supported by the UFCW, Our Walmart, has threatened to protest against Walmart's 8 p.m. opening on Thanksgiving Day, and what the group says are unfair labor conditions. The group has said protests could take place at 1,000 locations.

Walmart's labor issue is coming to a climax as another union fight, that of Hostess and its bakers, may come to a close this week. A bankruptcy hearing is scheduled to continue on Thursday, as Hostess' requested liquidation hangs in the balance.

Based in Bentonville, Ark., Walmart employs 1.3 million associates, and the company says only a small minority of workers, less than 0.0003 percent, are expected to protest on Black Friday.

"In fact, many of our associates have urged us to do something about the UFCW's latest round of publicity stunts because they don't think it's right that a few associates that are being coerced by the UFCW are being portrayed by the media as representative of what it's like to work at Walmart," Walmart national media relations director Kory Lundberg said in a statement.

Lundberg said "most of the numbers of people the UFCW claims at their events aren't even Walmart workers. They are union representatives and other union members."

Colby Harris, OUR Walmart member from Lancaster, Texas, fired back.

"Walmart is doing everything in its power to attempt to silence our voice. But nothing -- not even this baseless unfair labor practice charge -- will stop us from speaking out," he said in a statement.